Totally novice question: what are the pros/cons of using a finish for inside of a box? Is it just a matter of taste or is the extra work important for resiliency. In my case, I’ll be using shellac, and it’ll be a toolbox.

I prefinish the insides of all my boxes with shellac to keep glue squeeze out from sticking in those inside corners. Just be careful not to get shellac where you want glue adhesion. I do this on mitered boxes as well as box jointed ones.